How to Transcribe DNA to mRNA — Understanding the Genetic Code

If you have ever asked yourself how do you transcribe DNA to mRNA​, this article will help you to finally get a grip of transcription. Keep on reading to learn more about:

• How to transcribe DNA to mRNA;
• How to transcribe mRNA to DNA​; and
• Practical examples — e.g., how would the DNA sequence GCTATA be transcribed to mRNA​​?

Before we get into how to transcribe DNA to mRNA, let's take a closer look at what transcription is and why it matters.

Transcription is the first process that makes the genetic information in our cells accessible and translatable into functional proteins. It's an indispensable step, because without this process, cells could not produce the proteins necessary for survival. This is also why viruses are not considered truly living organisms, since they contain genetic material and proteins but rely entirely on a host's cellular machinery to carry out transcription. Transcription is the beginning of protein synthesis, which allows cells and the whole organism to function independently.

But how do you transcribe DNA to mRNA​? First, we need to understand the structure of DNA and RNA. Both molecules consist of bases, but as DNA is a double-stranded molecule, it consists of complementary base pairs:

• Adenine (A) — complementary to thymine (T);
• Cytosine (C) — complementary to guanine (G);
• Guanine (G) — complementary to cytosine (C); and
• Thymine (T) — complementary to adenine (A).

During transcription, DNA is used as a template to transfer its genetic information to the mRNA strand. The RNA polymerase creates a new pre-mRNA strand by adding bases complementary to the template DNA strand. However, RNA does not contain thymine; instead, uracil (U) becomes the complementary base to adenine (A).

You can find the particular transcription scheme in the transcription table below:

Now, let's take a look at an example: How would the DNA sequence G C T A T A be transcribed to mRNA? Let's apply the scheme from above:

G → C
C → G
T → A
A → U
T → A
A → U

So our mRNA sequence is C G A U A U — easy, isn't it?

Great, now we have the RNA sequence! The next step is translation to complete protein synthesis.

Now that we've understood the flow of protein synthesis: DNA → mRNA → protein, let's mix things up a little bit! Here's the plot twist — there is such a thing as reverse transcription. That means that mRNA is transcribed to DNA.

This process naturally occurs in some viruses (e.g., retroviruses) but is also widely used in molecular research. Some viruses have RNA genomes and, in order to use the host cell's transcription machinery, they must first convert their RNA into DNA.

In research, mRNA is often isolated because it reflects which genes are actively transcribed. However, mRNA is single-stranded and unstable, making it challenging to work with directly. Therefore, researchers use viral reverse transcriptase to convert mRNA into complementary DNA (cDNA), which is more stable and easier to manipulate.

It is essentially transcription — only in reverse. If you want to be sure how to transcribe mRNA to DNA, feel free to double-check with this reverse transcription table: